The present invention pertains to method and apparatus for anchoring bone screws into bones of living beings and injecting under high pressure materials that are high in viscosity.
One technique for inserting and anchoring bone screws relies on use of an expandable device that is inserted into a starter cavity produced by sharp mechanical means, which may include a drill, operating the expandable device to expand the size of the cavity, operating the expandable device to allow the device to contract, withdrawing the device from the expanded cavity, pumping some quick hardening, less viscous cement into the expanded cavity, inserting the desired screw into the cement-filled cavity, and removing the excess cement, if any, that is displaced by the insertion of the screw. This technique has been used in connection with screws that are inserted into the pedicle of the vertebra.
Because of the need to create the cavity to receive the cement, this procedure involves time and expense to create the cavity for the screw and cement. The use of a less viscous cement increases the risk that the cement will extravasate and leak into areas where it would cause harm to the patient.